Soybean plants of the genus Glycine max L. have long been recognized to be an important crop, which is being grown in many parts of the world. This crop is grown primarily for the seeds that are produced. These seeds may be used for planting or as a source of edible and industrial oils with the residue serving as a livestock feed supplement.
Modern agriculture practices are increasingly taking advantage of herbicides to eliminate unwanted weeds from soybean fields and to minimize the expense of tilling fields to remove unwanted weeds. Presently, there are no herbicides that kill on contact (post-emergent herbicides) that can be used with conventional soybean plants without causing excessive crop injury. The herbicide glyphosate is an effective non-selective post-emergent herbicide. Plant transformation/genetic engineering has been used in the past to modify soybean plants to incorporate resistance to the herbicidal effects of glyphosate.
Genetic engineering/plant transformation involves the incorporation of a gene for herbicide resistance into the chromosome of the soybean plant. Such procedures require special expertise and can be very costly. The “resistance” gene is part of a construct that is placed in the plant to impart herbicide resistance. In addition, the construct contains promoters that are responsible for activating the gene in select portions or in all parts of the plant. The presence or absence of these promoters is used to determine if the plant is the result of genetic engineering/plant transformation. The gene construct that is in commercially available in soybean plants includes the promoters, CaMV35S, and NOS marker gene. Representative prior publications that concern the use of genetic engineering to produce such herbicide resistance include U.S. Pat. Nos. 4,971,908; 5,145,783; 5,312,910; 5,352,605; 5,530,196; and 5,858,742.
It also has been proposed in the past to attempt to create some sulfonylurea herbicide resistance in soybean plants through the use of induced mutagensis. See, for instance, (a) “Molecular Strategies for Crop Protection”, by R. S. Chaleff et al., Pages 415 to 425 (1987), (b) “Soybean Mutants with Increased Tolerance for Sulfonylurea Herbicides”, by Scott A. Sebastian et al. Crop Science, 27, Pages 948 to 952 (1987), and (c) “Semidominant Soybean Mutation for Resistance to Sulfonylurea Herbicides”, S. A. Sebastian et al., Crop Science, 29, Pages 1403 to 1408 (1989). The resulting plants display no glyphosate herbicide resistance, often display limited resistant to sulfonylurea herbicide, and such herbicide is sometimes ineffective to kill weeds in view of acquired resistance to the sulfonylurea herbicide.
The objective of the present invention is to provide a new and reliable route for providing genetically-controlled herbicide resistance in soybean plants in the absence of induced mutagensis or the insertion of a foreign gene. A further objective of the present invention is to provide a soybean plant having genetically-controlled resistance that can be contacted with the herbicide in all stages of the life cycle of the plant and seeds capable of producing the same. The invention also provides a soybean plant that contains within its genome a naturally occurring genetic determinant that confers herbicide resistance that can be genetically mapped and physically isolated for use in breeding or biotechnological programs. Such genetic determinants represent novel genetic mechanisms for conferring herbicide resistance to host plants.
These and other objectives, as well as the scope, nature and utilization of the claimed invention will be apparent to those skilled in this area of technology from the following detailed description and appended claims.